I would like to note that you said average. That means on average most bbs will measur just under 6mm, but what about the other bbs that could measure just over 6mm (say 6.02 or so) that would mean that your getting friction which would slow your bbs velocity and would definitly drop your accuracy and would fail as a tight bore. If your buying a bag of 5000bbs your definitly going to have bbs in that bag that are alittle off measurment and with an aeg shooting full auto, some of those falty bbs are going to run through your barrel. If you go up to a 6.03mm you will definitly decrease the chances of faulty bbs. Coming to my conclusion, getting a 6.00mm tight bore is almost pointless for an aeg unless for shooting semi auto (sniper), it totally defeats the purpose of a tight bore barrel for and aeg. DON'T GET A 6.00MM TIGHT BORE FOR AND AEG THAT YOU SHOOT FULLY AUTOMATIC WITH!!!!!

There are no such things as airsoft snipers.

Anyway, that may be the case, but with higher quality bbs, like KSC Perfect ( I use AE ), I would doubt that would happen.

I never said that a prometheus wasn't compatible with the stock bucking. I was talking about using a 6mm tight bore. You will have some bbs in the batch that are alittle over 6mm and under 6mm. It is more rare that the bbs go over 6mm, but they do. Nothings truely perfect.

I never said that a prometheus wasn't compatible with the stock bucking. I was talking about using a 6mm tight bore. You will have some bbs in the batch that are alittle over 6mm and under 6mm. It is more rare that the bbs go over 6mm, but they do. Nothings truely perfect.

I'm sure some do, but I thought they did a quality check on high polished bbs. (KSC, AE)

They do, but do you think there going to take each bb look at it and measure them, even the machines can't catch every single bb and make sure it's perfectly 6mm. If they had the time to look at every bb the bb's wouldn't be able to be mass produced.